DOSE-RELATED CARDIOVASCULAR EFFECTS OF AMRINONE AND EPINEPHRINE IN REVERSING BUPIVACAINE-INDUCED CARDIOVASCULAR DEPRESSION

Background: To ascertain the efficacy of amrinone and epinephrine in r eversing bupivacaine-induced cardiovascular depression, we investigate d the time course of recovery of cardiac function with 3 doses of both agents after bupivacaine administration. Methods: In sevoflurane-anae sthetized dogs, bupivacaine was infused intravenously at 1 mg.kg(-1).m in(-1) until mean arterial pressure fell to 60 mmHg or less. The 3 dos es of amrinone (1, 2 and 4 mg.kg(-1)) or the 3 doses of epinephrine (2 , 5, and 10 mu g.kg(-1)) were administered as a bolus in randomized or der in each dog. Results: Amrinone improved maximum left ventricular d P/dt, a time constant of left ventricular isovolemic relaxation and ca rdiac index persistently and dose-relatedly. Amrinone increased heart rate and decreased left ventricular end-diastolic pressure and systemi c vascular resistance index. Amrinone at 1 and 2 mg.kg(-1) significant ly increased mean arterial pressure, but amrinone at 4 mg.kg(-1) did n ot. Epinephrine increased mean arterial pressure, maximum left ventric ular dP/dt, and systemic vascular resistance dose-relatedly. The durat ion of action of epinephrine, peaking at 1 min and subsequently decrea sing by 10 min after administration, did not differ among the groups. Epinephrine at all doses failed to improve a time constant of left ven tricular isovolemic relaxation and cardiac index. ECG evidence of seri ous ventricular dysrhythmias was seen in 1 out of 6 dogs after adminis trating each dose of amrinone and in 3, 3 and 5 out of 6 dogs after ad ministrating 2,5 and 10 mu g.kg(-1) of epinephrine, respectively. Conc lusion: Bolus amrinone may have a certain efficacy in reversing bupiva caine-induced cardiovascular depression, and improving cardiac contrac tility and relaxation dose-relatedly. In contrast to amrinone, bolus e pinephrine remains indispensable far resuscitation, causing a rapid, m assive, transient and dose-related rise in blood pressure. However, th e use of amrinone may be limited predominantly by a decrease in system ic vascular resistance, while the use of epinephrine may be limited pr edominantly by the generation of serious ventricular dysrhythmias and lack of effectiveness on cardiac index and on cardiac relaxation.